1. Field of the Disclosure
This disclosure relates to an ink-jet print apparatus and method adapted to prevent stain defects.
2. Description of the Related Art
Recently, a variety of flat panel display devices with reduced weight and volume have been widely used instead of cathode ray tube (CRTs). The flat panel display devices include liquid crystal display (LCD) devices, field emission display (FED) devices, plasma display panels (PDPs), and light emitting diode (LED) display devices. These flat panel display devices are applied to image display appliances such as televisions and computer monitors, in order to display lettering and a variety of images including moving images. Among these flat display devices, LCD devices have been used in a variety of fields because they allow electronic appliances to be light weight and thin and have an improved mass productivity.
More particularly, the LCD device of an active matrix type has superior image-quality and low electric power consumption. In addition, the active matrix LCD device has been more rapidly developed to be large-sized and highly defined due to recently secured mass producing technology and obtained research results.
The LCD device is manufactured using a liquid crystal panel formation process which involves producing a thin film transistor substrate, producing a color filter substrate, injecting liquid crystal between the substrates, and sealing the substrates, followed by a process of attaching a polarization plate, a driver substrate, and a backlight unit to the liquid crystal panel. The thin film transistor substrate includes a thin film transistor and a pixel electrode which are formed in each pixel. The color filter substrate includes a common electrode facing the thin film transistor substrate, as well as red, green, and blue filters formed opposite each pixel.
FIG. 1 is a planar view showing a color pixel included in a LCD device according to the related art. FIG. 2 is a cross-sectional view showing the color pixel of the LCD device taken along the line A-A′ shown in FIG. 1. As shown in FIG. 1, the LCD device includes a thin film transistor substrate 10, a color filter substrate 20, and liquid crystal (not shown) interposed between the substrates 10 and 20.
On the thin film transistor substrate 10, a plurality of gate lines 11 extending in a horizontal direction and a plurality of data lines 12 extending in a vertical direction are formed crossing each other. Each thin film transistor 13 is formed at each of the intersection of the gate and data lines 11 and 12. The thin film transistor substrate 10 includes a pixel electrode 14 formed on each pixel region which is defined by the crossing gate and data lines 11 and 12. The color filter substrate 20 includes a common electrode 24 opposite to all the pixel electrodes 14. Although it is not shown in the drawing, the color filter substrate 20 further includes color filters realizing a variety of colors.
The operation of LCD device with the above configuration can be explained as a change of the molecular alignment of the liquid crystal. More specifically, the thin film transistor 13 is turned on and allows a data voltage on the data line 12 to be applied to the pixel electrode 14 when a gate-on signal is applied to the gate line 11. At this time, a reference voltage (or a common voltage) is also applied to the common electrode 24. As such, the molecular alignment of the liquid crystal is changed by an electric field corresponding to a voltage difference between the data voltage on the pixel electrode 14 and the reference voltage on the common electrode 24.
As shown in FIG. 2, the thin film transistor substrate 10 includes two insulation films 15 and 16 formed on it. The insulation films are a gate insulation film 15 covering a gate line (not shown), and a passivation film 16 protecting a thin film transistor (not shown), respectively. The insulation films 15 and 16 are generally formed of silicon nitride. A data line 12, a semiconductor layer (not shown), and source/drain electrodes (not shown) are formed in the respective regions on the gate insulation film 15. Pixel electrodes 14 are formed on the passivation film 16.
On the other hand, the color filter substrate 20 includes a color filter layer 22 for realizing a variety of colors and a common electrode 24. The color filter layer 22 includes three different color filters arranged alternating with one another, even though a red color filter R and a green color filter G are shown in the drawing. The three different color filters consist of the three primary colors, respectively. A black matrix 21 is formed on a boundary region between the different color filters R and G adjacent to each other. The black matrix 21 blocks light penetrated through a liquid crystal on the boundary region which is not controlled by the pixel electrode 14. On the black matrix 21 and the color filter layer 22, an overcoat film 23 and the common electrode 24 are sequentially formed. The overcoat film 23 can be selectively used for applying superior step coverage to the formation of the common electrode 25, in spite of the topology of the color filter substrate 20 caused by the black matrix 21 and the color filter layer 22. In other words, it is not necessary to use the overcoat film 23. The common electrode 24 faces the pixel electrodes 14 on the thin film transistor substrate 10. A liquid crystal 30 is injected between the thin film transistor substrate 10 and the color filter substrate 20. The molecular alignment of the liquid crystal 30 changes direction according to a voltage which is applied between the common electrode 24 and the pixel electrode 14.
The related art LCD device as configured above has malfunctions on the color filter layer 22. Actually, the color filter layer 22 is formed by an ink-jet printing process of jet color filter materials into each sub-pixel. In this case, the topology (i.e., the surface state) of the color filter substrate causes a size difference between the color filters injected into the sub-pixels. Due to this, a stain defect is generated on an image displayed by the related art LCD device.